JP2016109780A - Optical scanning device and image formation device - Google Patents

Abstract

The present invention suppresses a decrease in the amount of laser light of an optical scanning device with a simple configuration. A semiconductor laser that emits laser light, a polygon mirror that reflects the laser light emitted from the semiconductor laser and changes the reflection direction of the laser light, and the laser light reflected by the polygon mirror are received. A BD sensor 6 that includes a light receiving unit and outputs a signal based on reception of the laser light by the light receiving unit, and the semiconductor laser emits the laser light at a timing based on the signal output from the BD sensor 6. Thus, in the optical scanning device that scans the photosensitive drum 8 with the laser beam reflected by the polygon mirror 4, the CPU 11 sets the light amount of the laser beam while scanning the photosensitive drum 8 based on the signal output from the BD sensor 6. Have [Selection] Figure 6

Description

  The present disclosure relates to an optical scanning device provided in an image forming apparatus such as a laser beam printer or a digital copying machine, and an image forming apparatus.

  The optical scanning device has various optical components (light source, deflecting means, lens, mirror, etc.). As the operation time of the optical scanning device increases, there is a risk that dirt such as dust adheres to these optical components or rust occurs. Due to such contamination and rust of the optical component, there is a possibility that the amount of laser light emitted from the optical scanning device via the optical component may be smaller than in the initial operation of the optical scanning device.

  In Patent Document 1, a density detection image is formed on a photoreceptor of an image forming apparatus by an optical scanning device, the density detection image is developed, and the developed toner image is read by a density detection unit. It is disclosed that the light quantity of the light source is set based on the above.

JP 2008-68509 A

  However, when the method disclosed in Patent Document 1 is used, it is necessary to form a density detection image, develop it with toner, and then detect it with a density detection unit. Therefore, in order to detect the density detection image, it is necessary to consume the toner because it is developed with toner, or it is necessary to provide a density detection unit.

  In view of the above problems, the present disclosure aims to disclose a configuration that suppresses a reduction in the amount of laser light of an optical scanning device with a simple configuration.

  The present disclosure includes a light source that emits laser light, a deflecting unit that reflects the laser light emitted from the light source and changes a reflection direction of the laser light, and a light receiving unit that receives the laser light reflected by the deflecting unit. And a signal output means for outputting a signal based on reception of the laser light at the light receiving section, and the light source emits the laser light at a timing based on a signal output from the signal output means. Thus, in the optical scanning device that scans the surface to be scanned with the laser beam reflected by the deflecting unit, the light amount of the laser beam during the scanning of the surface to be scanned based on the signal output from the signal output unit It has the control means which sets up.

  According to the present disclosure, it is possible to suppress a decrease in the amount of laser light of the optical scanning device with a simple configuration.

Schematic sectional view of the image forming apparatus Schematic perspective view of optical scanning device Partial perspective view near the BD sensor of the optical scanning device The figure which shows BD received light quantity, BD signal, laser drive signal The figure which shows BD received light quantity, BD signal, laser drive signal Block diagram showing control configuration for light intensity correction Diagram showing dirt on polygon mirror Block diagram showing the relationship between the optical scanning device and the image processing unit The figure which shows the light quantity correction control flow The figure which shows the light quantity correction control flow The figure which shows correction | amendment of the light quantity of the laser beam in the surface position of a photosensitive drum Diagram showing the relationship between drum surface light quantity and drum surface potential Schematic perspective view of optical scanning device

<First Embodiment>
[Image forming apparatus]
FIG. 1 is a diagram illustrating an image forming apparatus 101. An optical scanning device 100 to be described later is installed on the optical bench 103. The optical bench 103 is a part of the housing of the image forming apparatus 101. The image forming apparatus 101 includes an image forming unit, such as a process cartridge 108, a paper feeding unit 104 on which a transfer material P is placed, a paper feeding roller 105, a transfer roller (transfer unit) 106, and a fixing device (fixing unit). 107 is provided. The process cartridge 108 includes a photosensitive drum (photosensitive member) 8 that is an image carrier, a charging roller 108a, and a developing roller 108b. The transfer roller 106 and the photosensitive drum 8 are in contact with each other to form a transfer nip.

  The surface of the photosensitive drum 8 is charged by the charging roller 108a while rotating around the rotation axis, and then the optical scanning device 100 emits laser light and scans the surface to form a latent image. Thereafter, toner is adhered to the surface by the developing roller 108b, and the latent image becomes a toner image developed by the toner.

  On the other hand, the transfer material P is fed from the paper feed unit 104 by the paper feed roller 105, and the toner image formed on the photosensitive drum 8 is transferred by the transfer roller 106. Thereafter, the toner image on the transfer material P is fixed to the transfer material P by heat and pressure in the fixing device 107. The transfer material P on which the toner is fixed is output to the outside of the image forming apparatus 101 by the paper discharge roller 110.

[Optical scanning device]
Next, the optical scanning device 100 will be described. FIG. 2 is a schematic perspective view of the optical scanning device 100. FIG. 8 is a block diagram showing the relationship between the optical scanning device 100 and the image processing unit 50. The semiconductor laser unit 1 is formed by unitizing a semiconductor laser 1a (not shown) as a light source for emitting a laser beam L and its drive circuit 1b. A laser beam L emitted from the semiconductor laser 1a passes through a lens 20 having a collimator lens function and a cylindrical lens function, and an aperture stop 3, and passes through a plurality of reflecting surfaces 12 formed on a rotary polygon mirror (polygon mirror) 4. Incident on one of them. The polygon mirror 4 is rotationally driven in the direction of arrow A by the drive unit 5 and functions as a deflecting unit that deflects the laser beam L. The direction in which the laser beam L is reflected by the reflecting surface 12 is changed by the rotation of the polygon mirror 4. When the polygon mirror 4 is in a certain rotation phase, the laser beam L reflected by the reflecting surface 12 passes through the BD lens unit 14. The light enters the BD sensor 6 including the light receiving unit 10 (see FIG. 3). When the polygon mirror 4 is in another rotational phase, the laser beam L enters the fθ lens (scanning lens) 7 and enters the photosensitive surface (scanned surface) that is the surface of the photosensitive drum 8. This is an optical box 9 in which the optical members (semiconductor laser unit 1, lens 20, aperture stop 3, polygon mirror 4 and drive unit 5, BD sensor 6, fθ lens 7) described above are supported and positioned and fixed.

[Scanning of photosensitive drum with laser light]
Next, a method of scanning the photosensitive drum 8 with laser light by the optical scanning device 100 will be described with reference to FIGS. The laser beam L emitted from the semiconductor laser 1a of the semiconductor laser unit 1 is converted into substantially parallel light or convergent light in the main scanning direction by the lens 20 and converged light in the sub-scanning direction. Next, the laser beam L passes through the aperture stop 3 and is limited in its beam width, and forms an image on the reflecting surface 12 of the polygon mirror 4 in the form of a focal line extending long in the main scanning direction. Then, the reflection direction of the laser beam L on the reflecting surface 12 is continuously changed by the rotation of the polygon mirror 4, and the laser beam L is deflected. When the polygon mirror 4 is in a predetermined rotational phase, the reflected laser beam L is incident on the light receiving unit 10 of the BD sensor 6 as signal output means for outputting a BD signal without passing through a lens or the like. As shown in FIG. 3, the spot image S of the laser beam L on the surface of the BD sensor 6 has a circular shape. The spot image S moves in the direction of the arrow in the figure as the polygon mirror 4 rotates and passes over the light receiving unit 10. At this time, the BD sensor 6 outputs a BD signal based on the amount of light received by the light receiving unit 10, and the light emission start timing (image writing) of the light source based on the image data is based on the timing when the BD signal is output. Determined.

  When the polygon mirror 4 further rotates a predetermined amount, the reflected laser beam L passes through the fθ lens 7 and enters the surface of the photosensitive drum 8. The fθ lens 7 focuses the laser beam L and forms it as a spot image on the surface of the photosensitive drum 8. While the polygonal mirror 4 further rotates by a predetermined amount after the laser beam L starts to enter the fθ lens 7, the laser beam L continues to be incident on the surface of the photosensitive drum 8 through the fθ lens 7. The spot image moves in the scanning direction corresponding to the rotation direction of the polygon mirror 4. The scanning direction is parallel to the rotational axis direction of the photosensitive drum 8. The fθ lens 7 is designed at an imaging position of the laser beam L such that the spot image of the laser beam L moves in the scanning direction at a constant speed on the surface of the photosensitive drum 8.

  While the spot image of the laser beam L moves on the surface of the photosensitive drum 8 in the scanning direction, a driving current is supplied to the light source of the semiconductor laser unit 1 based on a laser driving signal (VIDEO signal) corresponding to image data to be formed. Is supplied and the light source is turned on. As a result, a latent image corresponding to the image data in the scanning direction is formed by scanning (main scanning) with the laser beam L.

  After a predetermined time has elapsed from the timing based on the output of the BD signal, the output of the laser drive signal is started from the image processing unit 50 toward the drive circuit 1b. Here, how to determine the output timing of the laser drive signal from the BD signal will be described. FIG. 4 shows three relationships between the amount of light received by the light receiving unit 10 and the amount of light received by the BD, the BD signal, and the laser drive signal. While the amount of received BD light (solid line) is above a certain slice level R1 (above a predetermined threshold), the BD sensor 6 outputs a BD signal. That is, the signal output of the BD signal rises during the period from timing ts to timing t4. The image processing unit 50 outputs a laser drive current after a desired period t1 has elapsed from the timing t0 at the center of the period during which the BD signal is output. The timing t0 corresponds to the timing when t2 / 2 has elapsed from the BD signal output start timing ts, where t2 is the BD signal output period, but the value of t2 at the timing t4 when the output of the BD signal ends (signal output falls). Can be calculated. For this reason, the image processing unit 50 starts time counting from the timing t4. After counting the elapse of a period t1-t2 / 2 obtained by subtracting the calculated period t2 / 2 from the desired period t1, a laser drive signal is output to the drive circuit 1b. Thus, since the timing of starting the laser drive signal is determined using the value of t2, the certain time t1 needs to satisfy t1> t2 / 2.

  In addition to the rotation of the polygon motor 4 described above, the photosensitive drum 8 rotates around the rotation axis, so that the spot image of the laser beam L moves relative to the photosensitive drum surface 8 in a direction perpendicular to the scanning direction ( (Sub scan). By rotating the polygon mirror 4 and the photosensitive drum 8 as described above, a two-dimensional latent image corresponding to image data is scanned and formed on the surface of the photosensitive drum 8 with the laser beam L.

  The BD signal output process and the subsequent scanning process using the laser beam L on the photosensitive drum 8 described above are performed for each reflection surface 12 as the polygon mirror 4 rotates.

[Light intensity correction method]
Next, light amount correction (light amount correction) of the laser beam L based on the BD signal will be described. Although the inside of the optical box 9 is covered with a lid (not shown), there are cases where the optical box 9 has a slight gap and cannot be completely sealed. For this reason, depending on the use environment, dust such as dust, toner and paper dust may enter the optical box 9. In addition, dust may remain in the optical box 9 during manufacture. In such a case, if the polygon mirror 4 is rotated, dust may adhere to the end of each reflecting surface 12 in the main scanning direction. In addition, the reflective surface 12 may be rusted due to aging.

  FIG. 7 shows a state where dust adheres to the polygon mirror 4. When the polygon mirror 4 rotates in the CW direction indicated by the arrow A (clockwise when viewed from above), the left side becomes negative pressure toward the reflecting surface 12 to entrain dust, and the dust adheres to the area indicated by Y1. . Further, the right side toward the reflecting surface 12 becomes positive pressure, dust is struck against the reflecting surface 12, and the dust adheres to the area indicated by Y2.

  Part of the position where the laser beam L condensed in the sub-scanning direction on the reflecting surface 12 of the polygon mirror 4 is reflected is indicated by H1 and H2. The position where the laser beam L is reflected on the reflecting surface 12 is displaced (moved) from the position indicated by H1 to the position indicated by H2 as the polygon mirror rotates. The laser beam L reflected near the position H1 enters near the scanning start position of the BD sensor and the photosensitive drum 8, and the laser beam L reflected near the position H2 forms an image near the scanning end position of the photosensitive drum 8. . Therefore, the dust adhering to the area Y1 reduces the amount of light near the scanning start time (start of writing of the image area) by the laser beam L from the BD sensor, and the dust adhering to the area Y2 is the scanning end time (end of writing of the image area). ) Reduce the amount of light in the vicinity. Such a decrease in the reflectance at both ends of the reflecting surface 12 causes unevenness in the density of the formed image in the scanning direction (the rotational axis direction of the photosensitive drum 8) corresponding to the rotational direction of the polygon mirror.

  In the configuration of Patent Document 1, it takes time until the density detection image is formed and detected, it is necessary to consume toner because the toner is developed with the toner for detection, or the density detection unit is installed in the image forming apparatus. Need to.

  Therefore, in the present embodiment, the light amount of the laser beam L is corrected based on the BD signal. FIG. 5 shows the three relationships of the amount of light received by the light receiving unit 10, ie, the amount of BD light received, the BD signal, and the laser drive signal. The solid line in FIG. 5 is an initial state in which the polygon mirror 4 is not dirty, and is the same as that shown in FIG. When the polygon mirror 4 becomes dirty and the reflectance decreases, the amount of BD light received decreases as shown by the dotted line in FIG. The signal output period of the BD signal (BD signal (2)) when the reflectivity is reduced is a period t3 shorter by 2 × Δt than that of the initial BD signal (BD signal (1)).

  Note that the scanning start timing (image writing) is a fixed time t1 from the timing t0 at the center of the BD signal (when the BD signal output period is t3, the timing at which t3 / 2 has elapsed from the rise of the BD signal output). . Even if the amount of BD light received decreases and the width of the BD signal decreases from t2 to t3, basically the timing t0 at the center of the BD signal does not change. For this reason, by the above-described control, it is possible to control so that the scanning start timing comes after a certain time t1 from the central timing t0 of the BD signal.

  Here, the values of the signal output periods t2 and t3 of the BD signal are related to the amount of BD light received, and the decrease in the reflectance of the polygon mirror 4 can be calculated from this value. The main factor that decreases the amount of the laser beam L irradiated to the photosensitive drum 8 in the optical scanning device 100 is a decrease in the reflectance of the polygon mirror 4 due to dust or the like. For this reason, if the decrease in the reflectance of the polygon mirror 4 can be calculated, the light quantity of the laser beam L applied to the photosensitive drum 8 can also be estimated. In order to increase the amount of change in the signal output period with respect to the change in the amount of BD light received, the spot image diameter W2 in the moving direction indicated by the arrow of the spot image S on the BD sensor 6 is set to the light receiving unit 10 of the BD sensor 6. It is preferable to make it larger than ½ of the width W1 in the moving direction.

  FIG. 6 is a block diagram showing a control configuration for performing light quantity correction. The BD signal output from the BD sensor 6 is output to the CPU 11 which is a control unit that controls light amount correction. The CPU 11 measures the BD signal output period. The CPU 11 is provided in a control circuit (not shown) provided in an image forming apparatus 101 different from the optical scanning apparatus 100, but may be provided in the optical scanning apparatus 100. The CPU 11 compares the measured BD signal output period with the reference value T. The reference value T corresponds to the BD signal output period when the reflectivity is lowered. When the CPU 11 operates to correct the amount of light when the amount of BD light received decreases to, for example, 80% of the initial state, the BD signal output period corresponding to the case of the amount of BD light received of 80% in the initial state Is set as a reference value T.

  The reference value T may be a design value determined in advance, or may be a value calculated by measuring the laser light quantity and the BD signal output period at the time of manufacture, or the output of the BD signal when the integrated image forming number is less than or equal to the predetermined number. It may be a value calculated by measuring the period. In any case, the reference value T is stored in a storage means (not shown).

  When the BD signal output period is shorter than the reference value T, the CPU 11 determines that the BD received light amount is lower than the reference received light amount, and performs the correction to increase the light amount of the semiconductor laser 1a. The light quantity target value output to the drive circuit 1b is corrected. In this case, the current value of the drive current is increased by correcting the light amount target value to be larger. In this way, the CPU 11 is a control means for controlling the light amount correction described above.

  Next, a light amount correction control flow executed by the CPU 11 will be described. FIG. 9 shows a light amount correction control flow. First, the current BD signal output period T1 is measured (step S1). Specifically, the BD signal output period is measured a plurality of times, and the average is set as the current BD signal output period T1. By doing in this way, the influence of the variation in the output of the BD signal at each reflecting surface 12 of the polygon mirror 4 can be eliminated. Next, the current BD signal output period T1 is compared with the reference value T (step S2). When it is determined that the current BD signal output period T1 is equal to or shorter than the reference value T (T1 ≦ T), the target value of the light amount of the semiconductor laser 1a is changed so as to increase the light amount of the laser beam L. (Step S3). Specifically, the light quantity of the laser beam L is controlled so that the drive current supplied to the semiconductor laser 1a by the drive circuit 1b is increased.

  The drive circuit 1b performs so-called APC (= auto power control) feedback control so that the amount of laser light output from the semiconductor laser 1a becomes a desired amount. This APC will be described. The amount of laser light output from the semiconductor laser 1a is received by a photodiode provided behind the semiconductor laser 1a, and a drive current is set so that this voltage value becomes a target value while monitoring a voltage value proportional to the amount of light received by the photodiode. Modulate.

  The CPU 11 corrects and sets the target value in the APC control to a value corresponding to the desired light amount, thereby setting the drive current to a desired current value. The target value correction amount is determined with reference to a data table in which the difference amount ΔT of the current BD signal output period T1 with respect to the reference value T is associated with the target value correction amount ΔV corresponding thereto. When it is determined that the current BD signal output period T1 is longer than the reference value T (T1> T), the target value of the light amount of the semiconductor laser 1a is not changed (step S4). The light amount correction can be performed by the flow as described above.

  As a modified example, as shown in the flow of FIG. 10, the target value correction amount is set to be increased by a fixed correction amount ΔV1 in step S3, and after the target value correction, the above-described steps S1 and S2 are executed again. Then, steps S1, S2, and S3 may be repeated until it is determined in step S2 that the current BD signal output period T1 is longer than the reference value T.

  The above-described light quantity correction control flow is executed every time in the startup process of the image forming apparatus 101 before image formation when the image forming apparatus 101 receives the image forming command and starts image forming. Alternatively, it may be executed every time a predetermined number of image formations are performed or an image formation job is performed a predetermined number of times.

  By such control, the light amount of the laser beam L that scans the photosensitive drum 8 is corrected. As described above, the CPU 11 determines that the polygon mirror 4 is more contaminated as the BD signal output period is shorter, and the light amount of the laser beam L applied to the surface of the photosensitive drum 8 is decreased. Make corrections to increase the amount of light.

  FIG. 11 is a diagram illustrating correction of the light amount (drum surface light amount) of the laser beam L at the position in the scanning direction on the surface of the photosensitive drum 8. The horizontal axis represents the position of the surface of the photosensitive drum 8 in the scanning direction, and the vertical axis represents the amount of the laser beam L at the surface position of the photosensitive drum 8. The solid line indicates the light amount characteristic in the initial state, the broken line indicates the light amount characteristic when the polygon mirror 4 is soiled, and the alternate long and short dash line indicates the light amount characteristic after the light amount correction. Due to the contamination of the polygon mirror 4, the amount of light is greatly reduced near the scanning start position (1) and near the scanning end position (2).

  In addition, the light receiving unit 10 of the BD sensor 6 is arranged on the upstream side in the scanning direction with respect to the scanning start position (2), and is reflected on the reflection surface 12 at a position closer to the end than the scanning start position (2). The received laser beam L is received. The closer the reflection surface 12 is to the end portion, the more easily it becomes dirty, and the amount of decrease in reflectance tends to be larger. Therefore, the value related to the amount of BD light received during the BD signal output period or the like This parameter is suitable for detecting with high sensitivity.

  In the present embodiment, since the light amount is corrected by the APC described above, the light amount increases almost uniformly at any position in the scanning direction. Regarding the amount of light correction, even if the amount of light at any of the scan start position, scan end position, and center position in the scan direction is set to the same light amount as the initial state or the lower limit value of the allowable light amount. good. However, in this embodiment, the average light amount in the scanning direction is set so as to be approximately the same as that in the initial state. That is, the correction amount is determined so that the light amount is larger at the center position in the scanning direction with a relatively high light amount than in the initial state, and the light amount is smaller at the scanning start position and the scanning end position with a relatively low light amount than in the initial state.

  This effect will be described. FIG. 12 shows the relationship between the light amount of the laser beam L (drum surface light amount) on the photosensitive drum 8 and the surface potential (drum surface potential) of the photosensitive drum 8 after being exposed to the laser beam L for a unit time. In the drum surface potential difference ΔV1 when the drum surface light amount is decreased by ΔP with respect to the design value and the drum surface potential difference ΔV2 when the drum surface light amount exceeds the design value and there is a ΔP light amount difference, ΔV1> ΔV2. Since the drum surface potential difference appears as uneven image density, if the same drum light intensity difference occurs, the image density unevenness may be less sensitive to the light intensity difference when the design light amount (initial value) is straddled. I understand. In this way, the light amount is corrected so that the light amount is larger at the center position in the scanning direction with a relatively high light amount than in the initial state, and the light amount is smaller at the scanning start position and the scanning end position with a relatively low light amount than in the initial state. Thereby, it is possible to effectively reduce density unevenness in the scanning direction.

  As described above, according to the present embodiment, by setting the light amount of the laser beam irradiated to the photosensitive drum 6 based on the BD signal, the light amount can be corrected as long as the BD sensor 6 is already provided. Therefore, there is no need to provide another sensor. Further, since the amount of light can be corrected without forming a toner image, toner consumption can be suppressed. Accordingly, it is possible to suppress a decrease in the amount of laser light of the optical scanning device 100 with a simple configuration.

<Other embodiments>
In the first embodiment, correction is performed based on the signal output period of the BD signal, but the present invention is not limited to this. That is, if the BD sensor 6 is configured to output a value corresponding to the BD light reception amount as a BD signal, a value corresponding to the maximum value of the BD light reception amount (P in FIG. 4) or a value corresponding to the BD light reception amount is set. You may correct | amend based on the value corresponding to the sum total of BD light reception amount integrated with time.

  Further, as shown in FIG. 13, instead of the lens 20, a lens 2 integrally including a lens unit having a collimator lens function and a cylindrical lens function and a BD lens unit 14 may be used. In this case, the laser beam L transmitted through the BD lens unit 14 is incident on the BD sensor 6.

  In addition, as shown in FIG. 11, the correction of the light amount is not set so that the light amount increases almost uniformly at any position in the scanning direction, but the correction amount of the light amount may be changed depending on the position in the scanning direction. In this case, a configuration is required in which the drive current supplied to the semiconductor laser 1a can be changed at a predetermined time interval (resolution) in one scan. In such a case, a profile of the correction amount of the drive current corresponding to the position in the scanning direction is created and stored in consideration of the light quantity characteristic related to the position in the scanning direction when the reflection surface of the polygon mirror 4 is dirty. The drive current may be corrected based on the BD signal and its profile.

  Also in such other embodiments, by setting the light amount of the laser beam irradiated to the photosensitive drum 6 based on the BD signal, it is possible to suppress a decrease in the light amount of the laser beam of the optical scanning device 100 with a simple configuration. Can do.

DESCRIPTION OF SYMBOLS 1 Semiconductor laser unit 1a Semiconductor laser 4 Polygon mirror 6 BD sensor 8 Photosensitive drum 10 Light-receiving part 11 CPU
12 reflective surface 100 optical scanning device 101 image forming apparatus

Claims (10)

A light source that emits laser light, a deflecting unit that reflects the laser light emitted from the light source and changes a reflection direction of the laser light, and a light receiving unit that receives the laser light reflected by the deflecting unit, A signal output unit that outputs a signal based on reception of the laser beam by the light receiving unit, and the light source emits the laser beam at a timing based on a signal output from the signal output unit, In the optical scanning device that scans the surface to be scanned with the laser beam reflected by the deflection unit,
An optical scanning apparatus comprising control means for setting a light quantity of laser light during scanning of the surface to be scanned based on a signal output from the signal output means.   The optical scanning apparatus according to claim 1, wherein the signal output from the signal output unit is a signal related to the amount of laser light incident on the light receiving unit.   3. The control unit according to claim 2, wherein when the light amount of the laser light incident on the light receiving unit is smaller than a reference value, the control unit sets the light amount of the laser light while scanning the surface to be scanned. Optical scanning device.   The signal output means outputs a signal when the amount of laser light incident on the light receiving unit is equal to or greater than a predetermined threshold value, and the control means outputs the signal to be scanned based on the length of the period during which the signal is output. The optical scanning device according to any one of claims 1 to 3, wherein the light amount of the laser beam is set while scanning the surface.   The optical scanning apparatus according to claim 4, wherein the period during which the signal is output from the signal output unit is longer as the amount of laser light incident on the light receiving unit is larger.   The light source emits laser light when supplied with a driving current, and the control means sets the light amount of the laser light by setting a current value of the driving current. The optical scanning device according to claim 5.   When the spot image of the laser beam reflected by the deflecting unit passes over the light receiving unit, the light receiving unit receives the laser beam, and the spot image moves while the spot image passes through the light receiving unit. The optical scanning apparatus according to claim 1, wherein the spot image has a width greater than a width of the light receiving unit with respect to a direction.   The optical scanning apparatus according to claim 1, wherein the laser beam reflected by the deflecting unit is incident on the light receiving unit without passing through a lens. An optical scanning device according to any one of claims 1 to 8, and a photosensitive member provided with a photosensitive surface as the scanned surface,
Based on the timing based on the signal output from the signal output means, the deflection means changes the reflection direction of the laser light, so that the spot image of the laser light irradiated on the photosensitive surface moves in the scanning direction. The image forming apparatus is characterized in that, with respect to the scanning direction, a position at which the laser beam starts scanning on the photosensitive surface is determined.   The image forming apparatus according to claim 9, wherein the light source emits laser light when supplied with a drive current, and the drive current is supplied to the light source based on image data.

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